Upper Cretaceous source rocks of northern and northwestern South America

Conference · Wed Mar 01 00:00:00 EST 1989 · AAPG Bull.; (United States)

OSTI ID:6017127

Talukdar, S; Gallango, O; Cassani, F; Vallejos, C

Organic carbon-rich, laminated, calcareous shales and limestones of Cenomanian to Campanian age are widespread in the polyhistory basins of Venezuela, Colombia, and Trinidad and are identified as the most important oil-generating source rocks in these basins. Available data on sedimentological, geochemical, and organic petrographic characteristics demonstrate that these source rocks are characterized by predominantly marine organic matter deposited in anoxic to near-anoxic marine environments. Marine transgressions due to eustatic sea level rise, with consequent flooding of available shelves of the northern and northwestern passive margin of the Cretaceous South American continent and resulting upwelling conditions, appears to be the key geologic control for the deposition of these laterally extensive source rocks. Significant vertical variations in geochemical properties are observed. These variations were caused by temporal changes in the influx of terrestrial organic matter and/or alternations of relatively oxic and anoxic conditions. Regional variations in organic carbon content, organic matter type, and oil potential broadly reflect the paleogeographic setting of the Cretaceous continental margin. The regionally extensive oil-prone source rocks became largely mature for hydrocarbon generation during the Tertiary, consequent to the development of the individual polyhistory basins. Rock-Eval pyrolysis data from several samples and results from hydrous pyrolysis experiments on some selected immature samples from the Venezuelan basins are used to define the oil-generating capacity, and kinetic parameters obtained from Rock-Eval experiments on the same samples are considered to outline the oil generation under the geological heating rates encountered in the sedimentary basins.

• Research Organization: Intevep, S.A., Caracas (Venezuela)
• OSTI ID: 6017127
• Report Number(s): CONF-890404-
• Journal Information: AAPG Bull.; (United States), Vol. 73:3; Conference: AAPG annual convention with DPA/EMD Divisions and SEPM, San Antonio, TX, USA, 23-26 Apr 1989
• Country of Publication: United States
• Language: English

Related Subjects

02 PETROLEUM
COLOMBIA
PETROLEUM DEPOSITS
SOURCE ROCKS
TRINIDAD AND TOBAGO
VENEZUELA
CONTINENTAL MARGIN
CRETACEOUS PERIOD
LIMESTONE
MATURATION
PYROLYSIS
SHALES
CARBONATE ROCKS
CHEMICAL REACTIONS
DECOMPOSITION
DEVELOPING COUNTRIES
GEOLOGIC AGES
GEOLOGIC DEPOSITS
ISLANDS
LATIN AMERICA
LESSER ANTILLES
MESOZOIC ERA
MINERAL RESOURCES
RESOURCES
ROCKS
SEDIMENTARY ROCKS
SOUTH AMERICA
THERMOCHEMICAL PROCESSES
WEST INDIES
020200* - Petroleum- Reserves
Geology
& Exploration